Catalyst and hydrocarbon conversion therewith



when

United St e Pm CATALYST AND HYDROCARBON CON- VERSION THEREWITH Alfred E. Hirschler, Springfield, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Application June 14, 1955 Serial No. 515,551

3 Claims. (Cl. 208117) This inevntion relates to catalytic compositions effective in catalytic processes for converting hydrocarbons. More particularly, this invention relates to new and improved catalytic compositions, their preparation, and to a process for converting hydrocarbons employing the new catalysts wherein a specific hydrocarbon fraction, boiling above the gasoline range, is converted to gasoline of high octane rating.

The conversion of various petroleum hydrocarbon frac. tions by processes such as cracking, reforming, hydroforming, and the like, using a variety of catalysts and reaction conditions, has been described. Cracking reac tions, for example, using a catalyst composed of silica and alumina which has been treated with hydrogen fluoride have been described. Such heretofore described processes, however, are not suitable for converting the hydrocarbon fraction boiling substantially within the range of. from about 375 F. to 500 F. to high octane gasoline in a single stage. Instead of achieving a'good yield of high octane gasoline, there is produced relatively large quantities of undesired products such as normally gaseous hydrocarbons, and the reduction of catalyst activity is rapid. It has heretofore been necessary to employ at least two stages to convert a petroleum hydrocarbou fraction boiling above the gasoline range, especially a fraction boiling within the range of from about 375 F. to 500 F., to high octane gasoline. Such processes usually involve a cracking stage wherein a portion of the hydrocarbons are converted to hydrocarbons boiling in the gasoline range, and a reforming, or hydroforming, stage to upgrade the octane'rating of the gasoline. In the upgrading stage, the use of two catalysts in separate reactors with a hydrocarbon separation step between the reactors, or the use of two catalysts in a single reactor, has heretofore been required.

An object of this invention is to provide new and improved catalytic compositions effective for converting hydrocarbons.

Another object is to provide a process for converting a hydrocarbon fraction boiling within the range of from about 375 -F. to 500 F. to high octane gasoline in a single stage and in good yield.

- A still further object is to provide a process for the preparation of new and improved catalysts.

Other objects and their achievement, in acocrdancc withthe-invention will be apparent from the following specification.

General A new catalytic composition has been discovered which givesimproved results in converting hydrocarbons. The new catalytic composition is a siliceous cracking catalyst, such as a natural clay or a synthetic composition containing silica and a promotor therefor. Before use the siliceous catalyst is treated with hydrogen fluoride and thereafter is leached with an aqueous solution of a water soluble salt of a promoter. When the siliceous catalyst is clay, it is preferred to use an aqueous solution of a water soluble aluminum compound, and when the siliceous catalyst is a synthetic silica-promoter composition it is preferred to use an aqueous solution of a water soluble compound of the promoter, as hereinafter described. The leached composition is dried and calcined to produce a catalyst in accordance wtih the invention. It has been found that the resulting new catalytic composition is especially eflective in converting relatively high boiling petroleum fractions, e.g., a fraction boiling within the range of from about 375 F. to 500 F., to gasoline hydrocarbons of high octane number, and that coke formation in the process is reduced to substantially a negligible value as compared to heretofore described processes.

The reactions involved in the process of the invention are primarily the cracking of the relatively high molecular weight hydrocarbons to hydrocarbons boiling in the gasoline range, and the dehydrogenation of hydrocarbons to produce hydrocarbons of higher octane number, such as the dehydrogenation of naphthenes to produce aromatic hydrocarbons. Hence, the'process of the present invention is conveniently designated herein as dehydrocracking. Other reactions, however, are involved and assist in producing the high octane hydrocarbons prepared by the process, such as the isomerization of paraffins to produce more highly branched chain paraflins of relatively highoctane number, and cyclization followed by dehydrogenation to produce aromatics from parafiins.

, A new method-for catalyst preparation has been discovered which gives an especially elfective catalyst in accordance with the invention. This new method of preparation is described hereinafter.

essentially of a siliceous cracking catalyst, such as a and'calcined. Preferably the calcining is performed withnatural clay or a composite of silica and a promoter therefor such as alumina, which has been treated with hydrogen fluoride and subsequently with an aqueous solution of a water soluble salt of a promoter, dried and calcined. For convenience, a siilca-alumina catalyst is hereinafter used to illustrate the invention which, however, is limited only as herein defined.

To illustrate the preparation of a catalytic composition of the invention, a silica-alumina cracking catalyst is contacted with an aqueous solution of hydrogen fluoride. Methyl alcohol or ethyl alcohol can be substituted in whole or in part for the water in preparing this solution. The quantity of hydrogen fluoride is advantageously about 10% by weight of the silica-alumina. It is preferred to use a quantity of solution such that drainage of excess solution is not necessary, i.e., a quantity that is substantially completely adsorbed by the silica-alumina. This procedure prevents the removal by leaching of any appreciable quantity of the components of the original siliceous catalyst. However, use of a quantity of solution suflicient to require a small amount of drainage does not deleteriously afiect the final catalyst. The resulting composition is then drained of excess solution, if necessary, and leached with an aqueous solution of a water soluble aluminum compound, such as aluminum nitrate. An alcohol can be substituted in whole or in part for the water, so long as the aluminum compound is soluble therein. The amount of aluminum compound is preferably at least the stoichiometric amount required to combine with the hydrogen fluoride used, and the amount of solution used is preferably suflicient to obtain substantial drainage thereof from the solid composition. After leaching with the aqueous solution of the aluminum compound, the treated silica-alumina is drained, dried the composition in contact with an oxygen-containing.

gas such as air, but an inert atmosphere can be used in this step with good results in some instances.

The preparation of the catalyst of the invention is.

preformed so that the leaching'step immediately follows the treatment with hydrogen fluoride, i.e., the hydrogen fluoride treated composition, prior to the leaching step, is not heated to an elevated temperature or contacted with a base, since such operation does not yield a catalytic composition having an activity comparable to the activity of the catalyst of the invention.

The final composition consists essentially of the original siliceous material, which is silica and alumina in the" above illustration, but may contain small quantities of fluorine. It is not known why the final composition gives. remarkably enhanced results. as. compared to the original silica-alumina composition, and as compared to the silica-alumina composition treated with hydrogen fluoride without subsequently leaching with an aqueous solution of an-aluminum compound. It is believed, however, that the treatment with hydrogen fluoride insome way disrupts the crystal structure of the original siliceous composition, such as by loosening silicon atoms (such as by forming SiF and by replacing such silicon atom with aluminum atoms. places a silicon atom in the lattice is believed to form. an active cracking center. By contrast, in known commercial cracking catalysts, the number of active cracking, sites is only a few percent or less of the total number of paring the composition of the present invention arewell.

known as crackingcatalysts, and heretofore described methods for their preparation may be employed in preparing the silica-alumina portion ofthe present catalyst- For example, the silica-alumina portion of the catalyst maybe prepared by impregnating silica with aluminum salts, by directly combining precipitated hydrated alumina and silica, or by joint precipitation of alumina and silica from aqueous solutions of their salts, and. by washing, drying, and heating the resulting composition. The resulting silica-alumina composition usually will have an activity index of'at least 30, and preferably from 4010 50. Activity index, as used herein, is a measure ofthe efliciency of a catalyst for cracking hydrocarbons and is determined by a method described'by Alexander, Pro- Each aluminum atom which re-- ceedings-Am. Pet. Inst. 27 (III) 51 (November 1947).

However, silica-alumina compositions having lower activity'indices can be used to prepare the catalyst of 'the invention for use in certain applications as hereinafter described. While the usual silica-alumina catalysts contain from about 10% to 25% alumina, useful results are obtained in accordance with-the invention with silicaalumina compositions containing from 2% to 98% alumina. The silica-alumina composition can be in :any

desired size or shape, such asgranules'ofirregular'size or pellets of uniform size formed by known-methods'su'ch as pelleting, extrusion or molding;

The silica-alumina composition, preferably after cal cining, is treated with hydrogen fluoride. In some irrstances the hydrogen fluoride-treatment, and the-subsequent leaching step, can advantageously be performed without .prior calcining of 'thesilicai-alumina. The quan tity of hydrogen fluoride used should be between 1% and 20% by weight ofthe silica-alumina composition.

The treatment .is advantageously performed byadmixing;

' lea-alumina toa' temperature of about 800" F. to

to 6 hours.

the silica-alumina with an aqueous solution of hydrogen fluoride, such as by adding the aqueous solution to the silica-alumina with agitation. The amount of the solution used is preferably not in excess of the amount required to wet the silica-alumina, so that it is unnecessary to drain excess solution therefrom, but some excess with drainage does not appear deleterious. The treatment may be performedin one or more steps, but the total amount of hydrogen fluoride used, exclusive of water, should be from 1% to 20%. by weight of the silicaalumina. If desired, anhydrous hydrogen fluoride, in gaseous or liquid phase, can be used to treat the silicaalumina. The period of time used for the treatment with hydrogen fluoride does-not appear critical, but will usually be from 15 minutes to 24 hours, but longer times are not deleterious.

After treatment with hydrogen fluoride, the silicaalumina composition is. leached withan aqueous solution of aLWater soluble :aluminum compound. Inorganic salts of aluminumsuch as aluminum nitrate, aluminum sulfate and aluminum chloride form suitable aqueous solutions. Aluminum nitrate is the preferred inorganic salt to'use. The quantity of solution used does not appear to be criticalbut must-be at least enough to obtain uniform leaching of the silica-alumina composition. The concentrationof the aluminum compound in the solution is preferably enough to. supply a quantity of aluminum equivalent to the. fluorine addedby the hydrogen fluor de (calculated as aluminum trifluoride), i.e.- a stoichiometric quantity of; aluminum is employed. A larger quantity isadvantageous'in some'instances, vsuch .as where substantially complete removal of fluorine from the silica-alumina is desired, in which case "from 2 to about '-li)i' times the stoichiornetrically-required amount, or even more, can advantageously be used. However, in some instances aslittle as A of the stoichiometrically required amountcanbe used' and good results obtained, .such as where a minor quantity of fluorine in the final catalytic composition isdesired- In any event, the quantity of the aluminum compound must be not less than this latter amount, namely, not less than enough to supply 1 of the quantityfof aluminum stoichiometrically equivalent to the fluorine supplied 'by the hydrogen-fluoride.

The leaching stepcan be conveniently performed by pasis'ng the aqueous solution of an aluminum compound over the hydrogen fluoride treated silica-alumina contained'in a vertical tube, thesolution being pa'ssedeither upwardly or downwardly through-the tube; This method can be performed with'a'siugle step or'wit'ha-pluralityof steps; dependingon the quantity of solution used" and theconcentration .of the aluminum compound in the solution. Ifdesired, leaching canbeaccomplish'ed by thoroughly admixing the hydrogen fluoride treated silica-alumina prior. to calcining, such as by mild heatin'gc Calcining is advantageously performed by heating the leached sil- 1200 F. in the presence of air for from about 'ISminutes. The composition from the calcining step isi' the. catalyst I of fthe :presentdnvention -.and:can.-be.used1in promoting hydrocarbon; reactions without further treatment,

It.is=-characteristic;-of. thepresenti invention that the catalystt preparation does not add a significant quantity of-aluminato the catalyst, the actual :amount'added being. less-than 1.% by weight under any; circumstances,,and.is

usually'less-than 0.5% by weight. Itisaalso-characteristic. thatlthe-fiuorine content rofwthc final composition-is.

If desired, the drained usually negligible, say less than 1% by weight, but a small quantity can be permitted to remain on the catalyst if desired, as above described. The fluorine content of the final catalyst should always be less than 2% by weight to obtain good results in accordance with the present invention.

- Natural siliceous clays can be substituted for the silicaalumina cracking catalyst as above described, and the re sulting catalytic compositions form a preferred embodiment of the invention. Suitable clays include, for example, the hydrated silicates of aluminum, and may include hydrated silicates of other metals such as iron or magnesium or combinations thereof, such as kaolin, fullers earth, attapulgite and the montmorillonite clays including bentonite. In this embodiment, it is preferred to use, after the treatment with hydrogen fluoride, an aqueous solution of a water soluble aluminum compound for leaching substantially as described for the silica-alumina composition.

Dehydrocracking The reactions involved in the present process for converting relatively high boiling petroleum hydrocarbons to gasoline hydrocarbons of high octane rating are primarily dehydrogenation and cracking, and hence the overall process is conveniently designated as dehydrocracking." The gasoline product preferably contains only hydrocarbons having a molecular weight lower than the hydrocarbons of the charge stock, and hence includes only the hydrocarbons which have been cracked in the process.

As above stated, the new catalytic compositions of the invention are especially suitable for dehydrocracking hydrocarbon fractions boiling in the range of from 375 F.

to 500 F. to gasoline hydrocarbons of high octane rating, heretofore described processes and catalysts being unsuitable for-this conversion. Accordingly, the use of the, present catalyst will be described in terms of this preferred embodiment.

Especially suitable charge stocks are straight-run fractions having a naphthene content of at least and preferably above 30%, say from about 30% to 75% by volume. Other fractions such as those obtained from catalytic cracking, and recycle gas oils in general, may be used.

In the process, temperatures within the range of from 450 C. to 540 C. give good'results and with the preferred hydrocarbon charge stock must be observed in order to obtain suitable conversion without excessive coke formation. The pressure is preferably maintained at about atmospheric pressure, but superatmospheric pressure up to about 100 p.s.i.g. can be used if desired. The space velocity must be maintained within the range of from about 0.5 to 3. It is preferred to employ a space velocity of from 0.8 to 1.5 since within this range there is obtained a high gasoline yield of high octane number. By space velocity, as used herein, is meant the liquid hourly space velocity, which is the liquid volume of hydrocarbons charged per volume of catalyst per hour.

In carrying out the process of the invention, it is preferred to pass the hydrocarbon charge through a bed of catalyst under the above conditions. By such operation the activity of the catalyst is gradually decreased, principally due to the deposition of carbonaceous materials thereon. Periodic regeneration of the catalyst, such as by discontinuing the operation, flushing the catalyst bed with an inert gas such as steam, flue gas, nitrogen, or the like, and burning off the carbonaceous materials by passing an oxygen containing gas, such as air, through the hot catalyst bed, is advantageously employed. When such treatment fails to restore sufiicient activity to the catalyst, regeneration as described with the additional steps of treating with hydrogen fluoride, leaching with an aqueous solution of a water soluble compound of a metal from the II, III and IV groups of the periodic system, and calcining substantially as described for the initial catalyst preparation restores the activity of the catalyst to substantially its initial activity.

Hydrogen preferably is not employed in the process, but a small partial pressure thereof is not deleterious. In some other uses of the present catalyst, however, an atmosphere of hydrogen is advantageous, especially where operation is at superatmospheric pressure, as hereinafter described.

Examples In order to illustrate a preferred catalytic composition of the invention and its use in dehydrocracking, a catalytic composition, in accordance with the invention, was prepared as follows, in which parts refers to parts by weight:

600 parts of a natural siliceous clay having an alumina content of about 40% by weight (calculated as A1 0 was admixed with 670 parts of ethyl alcohol and parts of an aqueous hydrogen fluoride solution containing 60 parts hydrogen fluoride. The admixture, after standing 20 hours at room temperature, was drained and then divided into two equal parts, designated as part A and part B.

Part A was dried and calcined in contact with air at 1000 F. for 3 hours. The resulting composition contained 6.6% by weight fluorine and is hereafter designated as catalyst A.

Part B was leached with a solution of 154 parts of aluminum nitrate (Al(NO -9H O) in 2000 parts of water by passing the solution down through a vertical tube containing the hydrogen fluoride treated clay. About 98.4% of the volume of the aqueous solution was recovered, the recovered aqueous solution containing substantially all of the fluorine originally introduced as aqueous hydrogen fluoride. The quantity of retained aluminum nitrate was suflicient to add not more than 0.36% by weight alumina to the clay. After draining, the leached composition was dried by mild heat and then calcined at about 1000 F. for about 3 hours in contact with air. The resulting catalyst contained 0.49% by weight fluorine and is hereafter designated as catalyst 13.

Both catalyst A and catalyst B were used to dehydrocrack the same relatively high boiling petroleum fraction. The petroleum fraction had a boiling range of from about 375 F. to '460" R, an aromatic content of about 13% by volume and a naphthene content of about 50% by' volume. The following conditions were employed during the contacting: temperature of catalyst=508 C., space velocity=l.01 to 1.02, pressure=atmospheric. The catalyst bed was regenerated after operation for 20 minutes by burning carbonaceous materials therefrom with a stream of air as above described. The results presented below were obtained on products collected over at least 7 cycles of catalyst regeneration. The results obtained were as follows:

Catalyst Catalyst A B Products:

Dry gas (wt. percent) Eydrocarbons of 4 carbon atoms (wt. percent) Gasoline (O -350 F.) (vol. percent)- Bottoms (vol. percent) Coke (wt. percent).

Octane rating of gasoline Liquid recovery (v01. perceut) Conversion (vol. percent) amasscontaining- ;about' 13% -by=weight .Al-2O .and abont.187.%. by weight SiO and hayingz'an II activity index of :about 46, was treated withhydrogen fluoride. 511 parts of the synthetic silica aluminaiin'theiformtot. pellets was treated? with about 37 'pans oft-hydrogen fluoride dissolved :in a mixture :of about I5702parts of'ethyltalcohol audBS partsof water by contact'ingifor 116 hours. The treated pellets were introduced into a vertically positioned, :column and leached f'or L1 hour lwithxa quantity of anaqueous solution containing 185.9 parts of aluminum. nitrate nonylhydrate per 814.1 partsofxwater to cover the pellets. The solution was drained. and a freshportion. of the same aqueous. solution ,percolated downwardlythrough the ,pellets,.ab.out. 101). parts of the solutionbeing used.

The leached composition was drained, .dried under infra-red heat at about 240' F., and then calcined for about 2.5. .hours. .at atemperature of. from. about 10100 F. to. 1200' E..in.contaet,with air.

The resulting composition consisted essentially of about 13% by weight Al fl and 87% by weight SiO with a minor quantity, .less than about 1% of fluorine. The so-formed catalytic composition, when used to convert hydrocarbons, gives good results in accordance with the process of the invention.

When other natural clays-or synthetic siliceous compositions are employed,.resu1ts substantially equivalent to those above described are obtained, but with such compositions containing a smaller percentage of alumina, the selectivity for. the production of ..gasoline.appears .to be even ,greater thans'hownby the foregoing data.

'The catalyst. of the .invention can be used .in other reactions involving the conversion tofhydrocarbons, such as .the catalytic crackingof gas, oil's, destructive hydro.- genation using elevated pressures in an atmosphere of hydrogen, reforming, and the like, in which catalytic conversion conditions known to be etfective in such processes give good results.

The invention claimed is:

1. A new composition of matter. etfectiveionconverting hydrocarbons prepared by contacting a natural. clay cracking catalyst with from 1% to 20% by weight hydrogen fluoride, leaching the resulting composition with an aqueouszsolution of a water soluble aluminum compound wherein the quantity of said aluminum compound .is at least M1 the stoichiometrictguantity required to vform aluminum triflu'oride by reaction of .said hydrogen fluoride .and saidalum-inum compound the volumeof the solution. being 'sufiiciently' great tonreduce: by leaching. the .fiuorine. content v:of: thercomposition .tor less tthanz-aoout 1%, and-calcining thefleachedcompositiou. in contact withan :oxygen contaitiin g gas.

2. A .new composition of .matter effective for converting hydrocarbons prepared by contacting a natural clay cracking catalyst withfrom 1% to 20% by weight of hydrogen .Ifluoride, leaching the .resultant composition: with anaqueous solution of a heat decomposable alumi num salt, the amount of said salt .in the solution being sufiicient to deposit-on the composition a smallxamount,

bill-1231685 than-one-percent of thecornposition, of thesalt,

the total volume of the solution being sufficiently great to reduce byleaching the fluorine content of the com position to less than about one percent, and calcining;

the leached composition in contact with .an oxygen-- containing gas..

.3. Process forxthe conversion oi-za hydrocarhonirac tion boiling in the range of from about 375 .F. to 5.00 F. to gasoline hydrocarbons which comprises contacting said hydrocarbon fraction ata temperature of from 450 C. to 540 C., a pressure of from atmospheric to 100.p.s:i;g. anda-space velocity of from'0;5 to 3 with a catalytic composition prepared by contacting a natural clay catalyist with from 1% to 2.0% by weight othydrogen fluoride, leaching the resultant composition -with;an.aqueous-- solution of a heat decomposable aluminum salt, the

amount a of salt .in the solution being sufiicient .to deposit on the. composition a small amount, but 1ess...than. one

percent of the composition, of thezsalt, the'total olume; of the solution being sufficiently great to reduce byleach ing the fluorinecontentto less thanabiout 1%, and .:ca1- cim'ng the leached composition :in contact with an oxygem containing gas. 

3. PROCESS FOR THE CONVERSION OF A HYDROCABON FRACTION BOILING IN THE RANGE OF FROM ABOUT 375*F. TO 500*F. TO GASOLINE HYDROCABONS WHICH COMPRISES CONTACTING SAID HYDROCARBON FRACTION AT A TEMPERATURE OF FROM 450*C. TO 540*C, A PRESSURE OF FROM ATMOSPHERIC TO 100 P.S.I.G. AND A SPACE VELOCITY OF FROM 0.5 TO 3 WITH A CATALYTIC COMPOSITION PREPARED BY CONTACTING A NATURAL CLAY CATALYIST WITH FROM 1% TO 20% BY WEIGHT OF HYDROGEN FLUORIDE, LEACHING THE RESULTANT COMPOSITION WITH AN AQUEOUS SOLUTION OF A HEAT DECOMPOSABLE ALUMINUM SALT, THE AMOUNT OF SALT IN THE SOLUTION BEING SUFFCIENT TO DEPOSIT ON THE COMPOSITION A SMALL AMOUNT, BUT LESS THAN ONE PERCENT OF THE COMPOSITION, OF THE SALT, THE TOTAL VOLUME OF THE SOLUTION BEING SUFFICIENTLY GREAT TO REDUCE BY LEACHING THE FLUORINE CONTENT TO LESS THAN ABOUT 1%, AND CALCINING THE LEACHED COMPOSITION IN CONTACT WITH AN OXYGENCONTAINING GAS. 